Urchin-type architecture assembled by cobalt phosphide nanorods encapsulated in graphene framework as an advanced anode for alkali metal ion batteries.

Urchin-type cobalt phosphide microparticles assembled by nanorod is encapsulated in graphene framework membrane (CoP@GF), and used as a binder-free electrode for alkali metal ion batteries. Electrochemical measurements indicate that this membrane exhibits enhanced reversible lithium, sodium, and potassium storage capabilities. Moreover, the energy storage properties of CoP@GF electrodes in alkali metal ion batteries display an order of Li > Na > K. DFT calculations on adsorption energy of CoP surfaces for Li, Na, and K indicated that CoP surfaces is more favorable to transfer electrons to Li atoms than Na and K, and the surface reactivity can be ordered as Li-CoP > Na-CoP > K-CoP, thus CoP@GF exhibit better storage capacity for lithium. This work provides experimental and theoretical basis for understand the electrochemical performance of cobalt phosphide-based membrane for alkali metal ion batteries.